Electronic device having a piezoelectric body for friction haptics

ABSTRACT

An electronic device is disclosed which includes a conductive layer for providing haptic feedback at an input surface of the electronic device. The conductive layer includes conductive particles within an organic compound, such as an epoxy. When the conductive layer is activated it may provide frictional or other tactile feedback at the input surface.

FIELD

The described embodiments relate generally to an electronic device whichprovides haptic output. More particularly, the present embodimentsrelate to providing electrostatic haptic output through coating asurface of an electronic device with a conductive coating and apassivation coating over the conductive coating.

BACKGROUND

Many electronic devices provide feedback to a user through variousstimuli, such as visual representations, audible sound, and tactileresponses. Feedback from an electronic device may enhance userexperience in interacting with the electronic device. For example, entryof inputs may be confirmed to a user through a visual alert, through aparticular sound, and so on.

Electronic devices may also provide tactile feedback to a user. As anexample, a mechanical button may provide feedback through the actions ofa spring, collapsible dome, or similar resistive component. In otherdevices, vibratory feedback may be provided to a user in contact withthe electronic device, such as through an actuating haptic motor.

SUMMARY

Embodiments described herein relate to an electronic device providingelectrostatic haptic feedback at an input surface of the electronicdevice. The electronic device may include a cover with an input surface,which may include a rigid transparent sheet. An electrostatic conductivelayer may be disposed over the transparent sheet, and a passivationlayer may be placed over the electrostatic conductive layer to form theinput surface. A part of the electrostatic conductive layer may beactivated through an electric field to provide friction feedback at theinput surface.

In an example embodiment, an electronic device includes a housingforming an external surface of the electronic device. A cover assemblyis coupled to the housing and defines an input surface. The coverassembly includes a cover sheet layer, a touch sensor layer coupled tothe cover sheet layer and configured to detect a touch on the inputsurface, and an electrostatic conductive layer coupled to the coversheet layer. The electronic device also includes processing circuitryconfigured to drive the touch sensor layer, causing at least a portionof the electrostatic conductive layer to experience an electric field.In response to the electric field, the electrostatic conductive layercauses variable friction feedback at the input surface.

In some cases, the processing circuitry drives the touch sensor layer,causing a region of the electrostatic conductive layer corresponding toa location of the touch to experience the electric field. A display maybe positioned below the cover assembly and configured to visuallyindicate a feedback region. The electrostatic conductive layer causesvariable friction feedback at a region of the input surfacecorresponding to the feedback region.

In another example embodiment, an electronic device includes a housing,a display at least partially enclosed by the housing, and a transparentcover assembly coupled to the housing and positioned over the display.The transparent cover assembly includes a cover sheet layer and a drivetouch electrode and a sense touch electrode coupled to and positionedbelow the cover sheet layer. The drive touch electrode and the sensetouch electrode operate to detect a location of a touch on the externalsurface.

An electrostatic conductive layer is coupled to and positioned above thecover sheet layer. The electrostatic conductive layer includesconductive particles in an organic matrix. The passivation layerincludes a dielectric material and forms an external surface of theelectronic device. The electrostatic conductive layer is configured toincrease friction between a finger and the external surface in responseto the drive touch electrode receiving a drive signal. A passivationlayer is coupled to and positioned above the electrostatic conductivelayer.

In some examples, the electrostatic conductive layer also includesnon-conductive particles, and the conductive particles are formed into aconductive region corresponding to the drive touch electrode surroundedby non-conductive particles. The organic matrix may include an epoxy andthe conductive particles may include at least one of indium tin oxide,tin oxide, aluminum zinc oxide, indium zinc oxide, or a transparentconductive oxide.

In another example embodiment, a method is provided for forming a coverassembly for an electronic device to provide electrostatic feedback onan input surface. The method includes the operations of forming anorganic compound and distributing conductive particles within theorganic compound. The organic compound is deposited over a cover sheetformed from a rigid transparent material. The organic compound is cured,and a dielectric layer is deposited over the organic compound. Themethod also includes coupling a touch sensor to the cover sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be readily understood by the following detaileddescription in conjunction with the accompanying drawings, wherein likereference numerals designate like elements.

FIG. 1 depicts an electronic device incorporating a hybrid conductivecoating for electrostatic haptic feedback according to the presentdisclosure.

FIG. 2A depicts a cross-section of a cover assembly, taken along sectionA-A of FIG. 1, illustrating providing electrostatic haptic feedbackthrough activation of an electrostatic conductive layer.

FIG. 2B depicts the cross-section of FIG. 2A, illustrating providingelectrostatic haptic feedback through activation of the electrostaticconductive layer.

FIG. 2C depicts the cross-section of FIG. 2A, illustrating providingelectrostatic haptic feedback through activation of the electrostaticconductive layer.

FIG. 2D depicts the cross-section of FIG. 2A, illustrating providingelectrostatic haptic feedback through activation of the electrostaticconductive layer.

FIG. 2E depicts the cross-section of FIG. 2A, illustrating providingelectrostatic haptic feedback through activation of the electrostaticconductive layer.

FIG. 3 depicts another cross-section of a cover assembly, taken alongsection A-A of FIG. 1, illustrating capacitive coupling of theelectrostatic conductive layer to a touch sensor layer.

FIG. 4 depicts another cross-section of a cover assembly, taken alongsection A-A of FIG. 1, illustrating particles within an electrostaticconductive layer and a passivation layer.

FIG. 5 depicts another cross-section of a cover assembly, taken alongsection A-A of FIG. 1.

FIG. 6A depicts a cross-section of a touch sensor, such as describedherein, particularly illustrating electrodes of the touch sensor and apiezoelectric haptic element disposed on the same surface.

FIG. 6B depicts the touch sensor of FIG. 6A when viewed along sectionline B-B.

FIG. 7A depicts a cross-section of a cover assembly, such as describedherein, particularly illustrating a piezoelectric haptic elementdisposed above a display.

FIG. 7B depicts a cross-section of a cover assembly, such as describedherein, particularly illustrating a piezoelectric haptic elementdisposed below a display.

FIG. 8A depicts an example particle arrangement for an electrostaticconductive layer.

FIG. 8B depicts another example particle arrangement for anelectrostatic conductive layer.

FIG. 8C depicts another example particle arrangement for anelectrostatic conductive layer.

FIG. 9A depicts a top view of an electronic device according to thepresent disclosure, illustrating electrostatic haptic feedback on aportion of an input surface.

FIG. 9B depicts another top view of an electronic device according tothe present disclosure, illustrating electrostatic haptic feedback onanother portion of an input surface.

FIG. 9C depicts another top view of an electronic device according tothe present disclosure, illustrating electrostatic haptic feedback onanother portion of an input surface.

FIG. 10 depicts an example method of forming a cover assembly for anelectronic device to provide electrostatic feedback at an input surface.

FIG. 11 depicts a schematic view illustrating components of anelectronic device according to the present disclosure.

The use of cross-hatching or shading in the accompanying figures isgenerally provided to clarify the boundaries between adjacent elementsand also to facilitate legibility of the figures. Accordingly, neitherthe presence nor the absence of cross-hatching or shading conveys orindicates any preference or requirement for particular materials,material properties, element proportions, element dimensions,commonalities of similarly illustrated elements, or any othercharacteristic, attribute, or property for any element illustrated inthe accompanying figures.

Additionally, it should be understood that the proportions anddimensions (either relative or absolute) of the various features andelements (and collections and groupings thereof) and the boundaries,separations, and positional relationships presented therebetween, areprovided in the accompanying figures merely to facilitate anunderstanding of the various embodiments described herein and,accordingly, may not necessarily be presented or illustrated to scale,and are not intended to indicate any preference or requirement for anillustrated embodiment to the exclusion of embodiments described withreference thereto.

DETAILED DESCRIPTION

Reference will now be made in detail to representative embodimentsillustrated in the accompanying drawings. It should be understood thatthe following descriptions are not intended to limit the embodiments toone preferred implementation. To the contrary, the described embodimentsare intended to cover alternatives, modifications, and equivalents ascan be included within the spirit and scope of the disclosure and asdefined by the appended claims.

The following disclosure relates to an electronic device which provideselectrostatic haptic feedback over an input surface of the electronicdevice. The electrostatic haptic feedback may provide tactile sensationsto a user in contact with the input surface, such as changes infriction. The electronic device may include a hybrid conductive coating,which may include inorganic conductive and non-conductive particleswithin an organic matrix. The hybrid conductive coating may include anelectrostatic conductive layer, and the device may be configured toapply an electrostatic charge to an input surface or other exteriorsurface of the device through the electrostatic conductive layer.

The electrostatic charge may alter or modify a tactile or touch-basedstimulus that is perceived by a user. In some cases, the tactilefeedback may cause an increased (or decreased) friction or surfaceroughness between an object (e.g., the user's finger) and theexterior/input surface as the object is moved along the input surface,for example by electrostatically attracting the user's finger to theinput surface.

The input surface may include an electrostatic conductive layer below apassivation layer. Electrostatic haptic feedback may be provided by anelectric field interacting with the electrostatic conductive layer toproduce an attractive force between the electrostatic conductive layerand an object (e.g., the user's finger). The passivation layer may be adielectric layer, sealing the electrostatic conductive layer frommoisture and the external environment while providing an electricallyinsulating surface between the electrostatic conductive layer and theuser's finger.

Additional components, such as touch sensors, may be placed below theelectrostatic conductive layer. In order to provide haptic feedback toan input surface, the electrostatic conductive layer may have a lowresistance level relative to the passivation layer. In some embodiments,it may also be desirable to avoid the electrostatic conductive layerinterfering with or blocking performance of other sensors, such ascapacitive touch sensor below the electrostatic conductive layer.

Accordingly, the electrostatic conductive layer may be formed withconductive particles within a non-conductive substrate. Thenon-conductive substrate may be an organic compound or matrix, such asan epoxy. For example, conductive particles may be dispersed within anorganic epoxy, and the epoxy may be deposited over a cover sheet layerand cured. In some embodiments, the conductive particles may bepatterned over the cover sheet layer, or the conductive particles may bedispersed.

A drive electrode may be positioned below the electrostatic conductivelayer. All or a portion of the conductive layer may be activated bydriving the drive electrode with an electrical signal. Driving the driveelectrode may cause an electric field to be generated, which may inducean attractive force in the conductive particles of at least a portion ofthe electrostatic conductive layer.

In some embodiments, the conductive particles nearest the driveelectrode may become electrically coupled to the drive electrode, whichmay localize the haptic feedback produced. In some embodiments, theelectrostatic feedback may not be localized. The drive electrode may beone of a set or array of drive electrodes. In some embodiments, thedrive electrode may also be a drive electrode of a capacitive touchsensor.

A particular embodiment of the input device may be a portable electronicdevice, such as a mobile telephone or tablet. The electronic device mayinclude a cover assembly coupled to a housing, with the cover assemblydefining an input surface. The cover assembly may be transparent andenclose a display.

The cover assembly includes a cover sheet layer and a conductive layerdeposited on the cover sheet layer. The conductive layer may provide avariable or configurable friction feedback to the input surface. Apassivation layer may be deposited over the conductive layer, which maybe a dielectric layer between the conductive layer and a finger or otherobject in contact with the passivation layer. A touch sensor may bedisposed below the cover sheet layer to detect the presence and/orlocation of an object on the input surface of the cover assembly.

The touch sensor may include drive touch electrodes and sense touchelectrodes, which may be arranged in a pattern. In some embodiments, thedrive touch electrodes may be formed as linear electrodes formed inrows, and the sense touch electrodes may be formed as linear electrodesin columns. A substrate may separate the drive touch electrodes and thesense touch electrodes. The drive touch electrodes and/or sense touchelectrodes may be monitored for changes in capacitance indicating atouch on the input surface.

Additionally, the drive touch electrodes may be driven with a hapticdrive signal in order to provide the electrical field to activate theconductive layer and provide electrostatic haptic feedback at the inputsurface. The haptic drive signal may induce a variable electrostaticcharge on the surface, which may produce sensations of higher and/orlower friction to a user operating the electronic device.

In some cases, an electronic device may incorporate a piezoelectric bodythat can be used as a haptic output element. The piezoelectric body mayalso serve as a dielectric layer separating sensing electrodes of acapacitive touch sensor, providing a single component to detect inputand provide haptic output. In such examples, a ground electrode of thepiezoelectric body can be used as a ground electrode of the capacitivetouch sensor.

As a result of these constructions, an input/output interface can bemanufactured to smaller dimensions, with fewer parts and materials, atincreased speed, and reduced cost. It may be appreciated that anyembodiment described herein—or any alternative thereto, or modificationthereof—can incorporate one or more input sensors that share one or moreelements, electrodes, components, or layers with a haptic outputelement.

Further, in some embodiments, a haptic output element of the coverassembly is configured to receive a voltage that is substantially higherthan a system voltage or reference voltage of the electronic device. Forexample, a haptic output element may be configured to drive anelectrostatic conductive layer positioned below the input surface with ahigh voltage signal in order to increase perceived friction between theuser's finger and the interface surface via electroadhesion. In anotherexample, a haptic output element may be configured to apply a highvoltage signal to a piezoelectric body in order to mechanically agitatethe interface surface (in-plane or out-of-plane) nearby the user'sfinger.

These and other embodiments are discussed below with reference to FIGS.1-11. However, those skilled in the art will readily appreciate that thedetailed description given herein with respect to these figures is forexplanatory purposes only and should not be construed as limiting.

FIG. 1 depicts an electronic device incorporating a hybrid conductivecoating for electrostatic haptic feedback according to the presentdisclosure. In the illustrated embodiment, the electronic device 100 isimplemented as a portable electronic device, such as a mobile phone.Other embodiments can implement the electronic device differently. Forexample, an electronic device can be a tablet computing device, a laptopcomputer, a wearable computing device, a digital music player, a kiosk,a stand-alone touch screen display, a mouse, a keyboard, and other typesof electronic devices that provide electrostatic haptic feedback at anexternal surface of the electronic device 100.

The electronic device 100 includes a housing 102 at least partiallysurrounding a display 104. The housing 102 can form an external surfaceor partial external surface for the internal components of theelectronic device 100. The housing 102 can be formed of one or morecomponents operably connected together, such as a front piece and a backpiece. Alternatively, the housing 102 can be formed of a single pieceoperably connected to the display 104.

The display 104 can provide a visual output to the user. The display 104can be implemented with any suitable technology, including, but notlimited to, a liquid crystal display element, a light emitting diodeelement, an organic light-emitting display element, an organicelectroluminescence element, and the like. A cover assembly 106 may bepositioned over the display 104 and define an input surface 108 externalto the electronic device 100.

A cover assembly 106 may be positioned over the front surface (or aportion of the front surface) of the electronic device 100. At least aportion of the cover assembly may function as an input surface 108 thatreceives touch and/or force inputs. In some embodiments, touch and/orforce inputs can be received across other portions of the cover assembly106 and/or portions of the housing 102. The cover assembly 106 mayinclude various layers and components, including a cover sheet layerformed of a suitable material, such as glass, plastic, sapphire, orcombinations thereof. Example cross-sections of the layers of the coverassembly 106 are described with respect to FIGS. 3-5.

The cover assembly 106 may additionally include a touch sensor fordetecting the presence and/or the location of one or more touches on theinput surface 108 of the electronic device 100. In many examples, thetouch sensor is a capacitive touch sensor configured to detect thelocation and/or area of one or more touches of a user's finger and/or apassive or active stylus on the input surface 108.

The cover assembly 106 may include a force sensor configured to detect alocation and/or amount of force applied to the input surface 108. Theforce sensor may be operably connected to force-sensing circuitryconfigured to estimate an amount of applied force. The force-sensingcircuitry may output a signal or otherwise indicate an input in responseto estimating an amount of force exceeding a threshold. The thresholdamount may be fixed or variable, and more than one threshold may beprovided corresponding to different inputs.

In a particular embodiment, the cover assembly 106 may also include ahybrid conductive coating, which may include inorganic conductive andnon-conductive particles within an organic matrix. The hybrid conductivecoating may include one or more layers for providing electrostatichaptic feedback at the input surface 108 of the electronic device 100.The hybrid conductive coating of the cover assembly 106 may include anelectrostatic conductive layer, which may be below a dielectricpassivation layer. When activated, the electrostatic conductive layermay produce an electrostatic charge on the input surface 108, which mayproduce tactile feedback to a user in the form of modified friction(e.g., variable friction feedback) as the user moves a finger across theinput surface 108 where electrodes are active. Example operations ofelectrostatic haptic feedback are described below with respect to FIGS.2A-2E.

The electrostatic conductive layer may include conductive particleswithin a substrate, such as an organic matrix or compound. In someexamples, the conductive particles may be arranged in a pattern, such asdescribed below with respect to FIGS. 8A-8C. The conductive particlesmay be individually controllable such that at a given time the level offriction may vary at multiple locations across the input surface 108,such as described below with respect to FIGS. 9A-9C. An example methodfor forming electrostatic feedback layers within the cover assembly 106is described below with respect to FIG. 10.

In some examples, friction or other haptic feedback may be providedthrough a piezoelectric body, such as a piezoelectric substrate. Apiezoelectric haptic output can, in some examples, be a localizeddecrease in perceived friction between the user's finger and theinterface surface. In some examples, the piezoelectric body may alsoprovide an insulating substrate for an input sensor, such as a touchsensor. Examples of an electronic device 100 incorporating apiezoelectric body for haptic output are further described below withrespect to FIGS. 6A-7B.

Various layers of the cover assembly 106 and/or the display 104 (such asthe cover sheet, display 104, touch sensor layer, force sensor layer,and so on) may be adhered together with an optically transparentadhesive and/or may be supported by a common frame or portion of thehousing 102. A common frame may extend around a perimeter, or a portionof the perimeter, of the display 104 and/or the cover assembly 106. Thecommon frame may be segmented around the perimeter, a portion of theperimeter, or may be coupled to the display 104 and/or the coverassembly 106 in another manner.

The common frame can be made from any suitable material such as, but notlimited to: metal, plastic, ceramic, acrylic, and so on. The commonframe, in some embodiments, may be a multi-purpose component serving anadditional function such as, but not limited to: providing anenvironmental and/or hermetic seal to one or more components of thedisplay 104, the cover assembly 106, or the electronic device 100;providing structural support to the housing 102; providing pressurerelief to one or more components of the display 104, the cover assembly106, or the electronic device 100; providing and defining gaps betweenone or more layers of the display 104 and/or the cover assembly 106 forthermal venting and/or to permit flexing of the layers in response to aforce applied to the input surface 108; and so on.

In some embodiments, each of the layers of the display stack may beattached or deposited onto separate substrates that may be laminated orbonded to each other. The display stack may also include other layersfor improving the structural or optical performance of the display 104,including, for example, polarizer sheets, color masks, and the like.Additionally, the display stack may include a touch and/or force sensorlayer for receiving inputs on the input surface 108 of the electronicdevice 100.

In many cases, the electronic device 100 can also include a processor,memory, power supply and/or battery, network connections, sensors,input/output ports, acoustic components, haptic components, digitaland/or analog circuits for performing and/or coordinating tasks of theelectronic device 100, and so on. For simplicity of illustration, theelectronic device 100 is depicted in FIG. 1 without many of thesecomponents, each of which may be included, partially and/or entirely,within the housing 102. Examples of such components are described belowwith respect to FIG. 11.

The electronic device 100 may also include one or more input devices110, which may be coupled to the housing 102 and/or the cover assembly106. The input device 110 may be a mechanical button, a soft button(e.g., a button that does not physically move but still accepts inputs),an icon or image on a display, and so on. The input device 110 mayreceive touch inputs and/or force inputs. In some embodiments, the inputdevice 110 may additionally or alternatively be operable to receivebiometric data from a user, such as through a capacitive fingerprintsensor, or another biometric sensor implemented with ultrasonic,infrared, multi-spectral, RF, thermal, optical, resistance,piezoelectric, and other technologies.

FIGS. 2A-2E depict a cross-section of a cover assembly, taken alongsection A-A of FIG. 1, illustrating providing electrostatic hapticfeedback through activation of the conductive layer. FIG. 2A illustratesan object, such as a user's finger 212, in contact with an input surface208 of a cover assembly 206. The user's finger 212 in contact with theinput surface 108 is illustrated at a second time in FIG. 2B, at a thirdtime in FIG. 2C, at a fourth time in FIG. 2D, and at a fifth time inFIG. 2E, as the user's finger 212 moves across the input surface 208.

As depicted in FIG. 2A, the cover assembly 206 may be depicted as asingle layer for clarity. In general, the cover assembly 206 may includea cover sheet layer, a touch sensor layer below the cover sheet layer,and additional layers above the cover sheet (e.g., an electrostaticconductive layer and a passivation layer) for providing electrostatichaptic feedback at the input surface 208. Examples of these additionallayers of the cover assembly 206 are described below with respect toFIGS. 3-5. At the first time depicted in FIG. 2A the cover assembly 206may not generate electrostatic haptic feedback.

At the second time, as depicted in FIG. 2B, the cover assembly 206 maygenerate electrostatic haptic feedback. For example, the cover assembly206 may include an electrostatic conductive layer, which may beelectrically coupled to a drive signal (such as depicted further withrespect to FIG. 3). The electrostatic conductive layer includes an arrayof conductive particles.

When activated, the electrostatic conductive layer may produce anelectrostatic charge 214 a on the input surface 208. The electrostaticcharge 214 a at the input surface 208 may induce a corresponding andopposite charge 216 a in the user's finger 212, which may generate anattractive force between the user's finger 212 and the input surface208. This attractive force may produce tactile feedback to a user in theform of modified friction as the user's finger 212 moves across theinput surface 208.

The sensation of the electrostatic haptic feedback may controllablycause the perception of a rough sensation, or alternatively a sandy,wavy, or similar sensation. The sensations may further be controlled toprovide more or less intense sensations. The electrostatic conductivelayer of the cover assembly 206 may cause a uniform type and intensityof frictional sensation (e.g., through a uniform electrostatic charge214 a), or the type and intensity may vary across the user input region212 a (e.g., through a varying electrostatic charge 214 a). For example,the sensation may become more intense as a user's finger nearsparticular regions of the input surface 208, such as a virtual key orbutton (e.g., an input region) visually indicated by the display. Thus,the cover assembly 206 may provide variable friction feedback at theinput surface 208.

In some embodiments, the electrostatic charge 214 a may be maintainedconstant, and in other embodiments the electrostatic charge may vary inpolarity and/or intensity. For example, the polarity of theelectrostatic charge may reverse. Accordingly, at the third time,depicted in FIG. 2C, the input surface 208 becomes electrostaticallyneutral (e.g., uncharged), and at the fourth time, depicted in FIG. 2D,the electrostatic conductive layer produces a reversed electrostaticcharge 214 b at the input surface 208.

Similar to the second time depicted in FIG. 2B, at the fourth time ofFIG. 2D the reversed electrostatic charge 214 b at the input surface 208induces a corresponding and opposite charge 216 b in the user's finger212, which may generate an attractive force between the user's finger212 and the input surface 208. The feedback sensations perceived by theuser through the alternating electrostatic charges 214 a, 214 b may becontrolled through changing the intensity and/or the frequency of theelectrostatic charges 214 a, 214 b.

Finally, at the fifth time, depicted in FIG. 2E, the input surface 208of the cover assembly 206 may become electrostatically neutral (e.g.,uncharged). In some examples, the electrostatic conductive layer maycease to produce the electrostatic charge (e.g., 214 a, 214 b) on theinput surface 208 in response to changes in controlling signals. Inother examples, only a portion of the input surface 208 may beelectrostatically charged, and the user's finger 212 may move to anotherportion of the input surface 208 which is not electrostatically charged,where the user ceases to perceive the increased friction sensation.

FIG. 3 depicts another cross-section of a cover assembly, taken alongsection A-A of FIG. 1, illustrating capacitive coupling of theconductive layer to a touch sensor layer. The cover assembly 306includes a cover sheet layer 322, an electrostatic conductive layer 320,a passivation layer 318, and a touch sensor 332.

At least a portion of the cover assembly 306 can function as an inputsurface 308 that receives touch and/or force inputs. The cover assembly306 may also produce haptic feedback to an object, such as a user'sfinger 312, in contact with the input surface 308. Haptic feedback maybe produced as an electrostatic haptic feedback, which may cause theuser to perceive changes in friction between the user's finger 312 andthe input surface 308.

Generally, the cover sheet layer 322 provides structural rigidity to thecover assembly 306, and may additionally enclose and protect the touchsensor 332 and a display (omitted from FIG. 3 for clarity). The coversheet layer 322 may be formed from a suitable dielectric material, suchas glass, plastic, sapphire (alumina), acrylic, ceramic, and othernon-conductive materials or combinations of materials. In someembodiments, such as a cover assembly 306 positioned over a display, thecover sheet layer 322 may be transparent. In other embodiments, thecover sheet layer 322 may be formed from an opaque material and/orinclude an opaque layer, such as an ink layer.

While in these examples the term “cover assembly” may refer to a coverfor a display of a portable electronic device, it should be understoodthat the term “cover assembly” may also refer to another input surface,such as a trackpad of a laptop computer or a portion of a housing (suchas the housing 102 depicted in FIG. 1). In some examples, the coverassembly 306 may enclose a virtual keyboard having dynamicallyadjustable input regions, which may be indicated through electrostatichaptic feedback provided by the electrostatic conductive layer 320.

An electrostatic conductive layer 320 may be coupled to the cover sheetlayer 322, and a passivation layer 318 may be coupled to theelectrostatic conductive layer 320. For example, the electrostaticconductive layer 320 may be deposited onto a top surface of the coversheet layer 322 facing outward from the electronic device. Thepassivation layer 318 (which may be an insulating layer) may likewise bedeposited over the electrostatic conductive layer 320.

The electrostatic conductive layer 320 may be formed with conductiveparticles within a non-conductive compound, such as described furtherwith respect to FIG. 4. As an example, conductive particles may bedispersed within an organic epoxy, and the epoxy may be deposited overthe cover sheet layer 322 and cured to form the electrostatic conductivelayer 320. The passivation layer 318 may be formed with non-conductiveparticles within a similar compound, such as described further withrespect to FIG. 4

In some embodiments, the electrostatic conductive layer 320 may beindirectly electrically charged, such as through a capacitive couplingto another layer or component of the cover assembly 306. For example, atouch sensor 332 positioned below the cover sheet layer 322 may includeone or more drive touch electrodes 326 and sense touch electrodes 330separated by an insulating substrate 328. A drive touch electrode 326may be coupled to a drive signal, which may induce an electric field,capacitively coupling the drive touch electrode 326 to at least aportion of the electrostatic conductive layer 320.

Due to the electric field coupling the drive touch electrode 326 to theelectrostatic conductive layer 320, the electrostatic conductive layer320 becomes electrostatically charged. The electrostatic chargegenerates or increases an attractive force between the electrostaticconductive layer 320 and a user's finger 312, which may be due to acapacitive coupling between the user's finger 312 and the electrostaticconductive layer 320. The passivation layer 318 may act as an insulatinglayer separating and facilitating the capacitive coupling of the user'sfinger 312 and the electrostatic conductive layer 320.

The attractive force between the user's finger 312 and the electrostaticconductive layer 320 may cause the user's finger 312 to be pulledagainst the input surface 308 (e.g., against the passivation layer 318).This may in turn increase the friction between the user's finger 312 andthe input surface 308 as the user's finger 312 slides along the inputsurface 308. The aforementioned attractive force is generallyperpendicular to the direction in which the user's finger 312 movesalong the input surface 308. Accordingly, when the attractive force ispresent, the user's finger is drawn into greater contact with the inputsurface 308, thereby increasing friction between that layer and theuser's finger 312 (or other object contacting the layer).

The sensation of friction induced by the electrostatic conductive layer320 may controllably cause a user to perceive a rough sensation, oralternatively a sandy, wavy, or similar sensation. The sensations mayfurther be controlled to provide more or less intense sensations. Theelectrostatic conductive layer 320 may cause a uniform type andintensity of frictional sensation, or the type and intensity may varyacross the input surface 308 as different drive touch electrodes 326receive distinct drive signals. For example, the sensation may becomemore intense as a user's finger 312 nears a given region, such as avirtual key or button (e.g., an input region). In some examples,distinct input regions may be driven by distinct drive signals, suchthat the intensity or sensation at a first input region is distinct fromthe intensity and/or sensation at a second input region.

The drive touch electrodes 326 may be controlled by processing circuitryand/or a signal generator (described further below with respect to FIG.11). Each of the drive touch electrodes 326 may be individuallycontrolled, or a group of drive touch electrodes 326 may be controlledtogether. The control circuitry may apply a drive signal (e.g., anelectrical signal) to a drive touch electrode 326 (or group of drivetouch electrodes 326) to activate and/or energize all or a portion ofthe electrostatic conductive layer 320. The drive signal may induce anelectrostatic charge or potential (e.g., through capacitive coupling)within a corresponding portion of the electrostatic conductive layer 320(e.g., a portion of the electrostatic conductive layer 320 substantiallyabove the drive touch electrode 326 receiving the drive signal).

The processing circuitry may cause the signal generator to applydistinct signals (e.g., by varying a voltage or current waveform) todifferent drive touch electrodes 326. This results in differentelectrostatic charges between one portion of the electrostaticconductive layer 320 and another, such that the attractive force (andtherefore friction) varies as a user's finger moves along the inputsurface 308.

In some examples, the processing circuitry may additionally beelectrically coupled to the touch sensor 332. The touch sensor 332 maydetect the location of one or more objects, such as the user's finger312, in contact with the input surface 308. As a result of the detectedtouch on the input surface, the processing circuitry may cause a drivesignal to be coupled to one or more drive touch electrodes 326 (e.g., bycausing the signal generator to transmit a drive signal to the drivetouch electrodes 326) at a location corresponding to the detected touch.This may, in turn, generate friction feedback at a portion of the inputsurface 308 corresponding to the detected touch.

In other examples, the processing circuitry may operate the drive touchelectrodes 326 in concert with other components of the electronicdevice, such as a display (e.g., display 104 depicted in FIG. 1). Forexample, the display may visually indicate a location of a feedbackregion, such as a virtual key or button, or an image or icon displayed(e.g., a region that appears rough visually). A drive signal may be sentto a drive touch electrode 326 at a location corresponding to thefeedback region, which may cause frictional feedback to be perceived bya user at the location of the feedback region (e.g., by causing a roughsensation over the region that appears rough).

In order to create perceptible friction sensations to a user, drivetouch electrodes 326 may be energized with electrical drive signals ofapproximately 100 to 400 volts (or more, depending on the sizes andmaterials of the adhesive layer 324, the cover sheet layer 322, theelectrostatic conductive layer 320, and the passivation layer 318) andfrequencies of approximately 100 to 500 Hertz. Varying the voltage andwaveform of the drive signal may generate varying sensations (e.g.,rough, sandy, wavy) and intensity levels to a user. For example,increasing the voltage of the signal to a drive touch electrode 326 mayincrease the attractive force between the user's finger 312 and theelectrostatic conductive layer 320, which in turn causes a more intensesensation of friction.

As described above, the touch sensor 332 may be formed from an array ofdrive touch electrodes 326 disposed on an insulating substrate 328, andmay additionally include an array of sense touch electrodes 330 disposedon the insulating substrate 328. The drive touch electrodes 326 andsense touch electrodes 330 are configured to detect the location of afinger or object on or near the cover sheet layer 322.

The touch sensor 332 may operate in accordance with a number ofdifferent sensing schemes. In some implementations, the touch sensor 332may operate in accordance with a mutual-capacitance sensing scheme.Under this scheme, the drive touch electrodes 326 may be substantiallylinear transparent conductive traces disposed on a first surface of theinsulating substrate 328, the traces spanning along a first direction.The sense touch electrodes 330 may be intersecting conductivetransparent conductive traces disposed on a second, parallel surface ofthe insulating substrate 328, the traces spanning along a seconddirection transverse to the first direction. The touch sensor 332 isconfigured to detect the location of a touch by monitoring a change incapacitive or charge coupling between pairs of intersecting drive touchelectrodes 326 and sense touch electrodes 330.

In another implementation, the touch sensor 332 may operate inaccordance with a self-capacitive sensing scheme. Under this scheme, thetouch sensor 332 may include an array of drive touch electrodes 326,which may be capacitive electrodes or pads disposed on a surface of theinsulating substrate 328. The drive touch electrodes 326 may beconfigured to detect the location of a touch by monitoring a change inself-capacitance of a small field generated by each drive touchelectrode 326. In other implementations, a resistive, inductive, orother sensing scheme could also be used, and in some of theseembodiments another component may drive the electrostatic conductivelayer 320.

The drive touch electrodes 326 and sense touch electrodes 330 may beformed by depositing or otherwise fixing a transparent conductivematerial to the insulating substrate 328. Potential materials for theinsulating substrate 328 include, for example, glass or transparentpolymers like polyethylene terephthalate or cyclo-olefin polymer.Example transparent conductive materials includepolyethyleneioxythiophene, indium tin oxide, carbon nanotubes, graphene,piezoresistive semiconductor materials, piezoresistive metal materials,silver nanowire, other metallic nanowires, and the like. The transparentconductors may be applied as a film or may be patterned into an array onthe surface of the substrate using a suitable disposition technique suchas, but not limited to: vapor deposition, sputtering, printing,roll-to-roll processing, gravure, pick and place, adhesive,mask-and-etch, and so on.

The touch sensor 332 may be coupled to the cover sheet layer 322 throughan adhesive layer 324, which may be an optically clear adhesive. In someembodiments, the adhesive layer 324 may be omitted and all or a portionof the touch sensor 332 may be formed directly on the cover sheet layer322 (e.g., by depositing an array of drive touch electrodes 326 directlyonto a bottom surface of the cover sheet layer 322).

It should be understood that FIG. 3 presents a cross-sectional viewwhich may omit certain components for clarity. For example, the coverassembly may be coupled to a display and additional layers. Theelectronic device may also include additional components and structures,such as the components depicted in FIG. 11, support structures, and thelike. In some embodiments, the arrangement of the layers depicted mayalso vary, in which some layers may be positioned differently relativeto others (such as depicted in FIG. 5), additional layers may beincluded, or some layers may be omitted.

Turning to FIG. 4, the electrostatic conductive layer and thepassivation layer may be formed from particles within a compound. FIG. 4depicts another cross-section of a cover assembly, taken along sectionA-A of FIG. 1. The cover assembly 406 may include a cover sheet layer422, which may provide structural rigidity and support to othercomponents of the cover assembly 406. A touch sensor 432 may be coupledto a bottom of the cover sheet layer 422 (e.g., internal to theelectronic device).

An electrostatic conductive layer 420 may be coupled to a top of thecover sheet layer 422, and a passivation layer 418 may be coupled to atop of the electrostatic conductive layer 420 (e.g., forming an externalsurface of the electronic device). The electrostatic conductive layer420 may be formed with conductive particles 438 and non-conductiveparticles 436 within a non-conductive compound, such as an organicmatrix 440.

In some examples, the organic matrix 440 may be an epoxy. The organicmatrix 440 may be formed with any appropriate epoxy resin, such asbisphenol A resins, bisphenal F resins, novolac resins, aliphaticresins, glycidylamine resins, and so on. In some embodiments, thematerial of the organic matrix 440 may be selected to enhance theperformance of the cover assembly 406, such as impact resistance. In aparticular embodiment, the cover assembly 406 may enclose a display, andthe organic matrix 440 may be formed from an optically transparentepoxy.

The conductive particles 438 may be formed from transparent conductivematerials, such as indium tin oxide, tin oxide, aluminum zinc oxide,indium zinc oxide, or a transparent conductive oxide. In embodiments inwhich the cover assembly 406 is opaque, the conductive particles 438 maybe formed from opaque conductive materials, such as gold, copper,aluminum, tin, and other combinations and alloys of conductivematerials. The non-conductive particles 436 may be formed from one ormore suitable transparent non-conductive materials. In embodiments inwhich the cover assembly 406 is opaque, the non-conductive particles 436may be formed from opaque materials.

In some embodiments, the conductive particles 438 may be disposed withinthe organic matrix 440 at a sufficient density to enable a sufficientelectrostatic charge to be placed on the electrostatic conductive layer420 to produce frictional haptic feedback at the input surface 408.However, if the conductive particles 438 are disposed at a uniform highdensity, the electrostatic conductive layer 420 may become anelectromagnetic shield, undesirably blocking the operation of the touchsensor 432 and other components of the electronic device.

Accordingly, non-conductive particles 436 and conductive particles 438may be included within the organic matrix 440 to ensure theelectrostatic conductive layer 420 operates to produce haptic feedbackand does not interfere with the operation of other components. Forexample, the conductive particles 438 and non-conductive particles 436may be disposed within the organic matrix 440 such that theelectrostatic conductive layer 420 has a resistance of between 1MΩ-per-square (one megaohm-per-square) and 100 MΩ-per-square (onehundred megaohms-per-square).

In some embodiments, the conductive particles 438 and non-conductiveparticles may be patterned to enhance the operation of the electrostaticconductive layer 420 and reduce interference with the operation of othercomponents. Examples of such patterns are described below with respectto FIGS. 8A-8C.

The electrostatic conductive layer 420 may be formed over the coversheet layer 422 in an appropriate manner. For example, the organicmatrix 440 may be formed as an epoxy resin, and conductive particles 438and non-conductive particles 436 may be added to the organic matrix 440.The organic matrix 440 may then be deposited onto the cover sheet layer422 and cured to form a hardened electrostatic conductive layer 420. Theformation of the electrostatic conductive layer 420 is further describedbelow with respect to FIG. 10.

The passivation layer 418 may be a suitable dielectric layer, which mayseal the electrostatic conductive layer 420 and define the input surface408, which may be an external surface of the electronic device. In someembodiments, the passivation layer 418 may be formed as a single uniformlayer, and in other embodiments the passivation layer 418 may benon-uniform and/or formed as multiple layers of distinct materials orcombinations of materials. In some examples, the passivation layer 418may include an organic or inorganic film, which may be bonded to theelectrostatic conductive layer 420 through an adhesive or otherappropriate technique.

In a particular embodiment, the passivation layer 418 may be formed froman organic matrix 444, such as an epoxy resin. The epoxy resin may bethe same as the organic matrix 440 of the electrostatic conductive layer420, or it may be a distinct epoxy resin having material properties toprovide a durable external surface of the cover assembly 406 and theelectronic device. The organic matrix 444 may be formed from atransparent epoxy resin, and may additionally include non-conductiveparticles 442.

The non-conductive particles 442 may be formed from one or more suitabletransparent non-conductive materials. In some embodiments, thenon-conductive particles 442 may be formed from materials which improvethe hardness, rigidity, scratch resistance, and other features of thepassivation layer 418, such as silicon carbide or a diamond-like carbon.In embodiments in which the cover assembly 406 is opaque, thenon-conductive particles 442 may be formed from opaque materials.

The passivation layer 418 may be formed over the electrostaticconductive layer 420 in an appropriate manner. For example, the organicmatrix 444 may be formed as an epoxy resin, and non-conductive particles442 may be added to the organic matrix 444. The organic matrix 444 maythen be deposited onto the electrostatic conductive layer 420 and curedto form a hardened passivation layer 418. In some embodiments, thepassivation layer 418 may form the input surface 408, while in otherembodiments additional coatings or layers may be added to thepassivation layer 418, such as oleophobic coatings, anti-glare coatings,and so on. The formation of the electrostatic conductive layer 420 isfurther described below with respect to FIG. 10.

FIG. 5 depicts another cross-section of a cover assembly, taken alongsection A-A of FIG. 1. The cover assembly 506 includes a cover sheetlayer 522, an electrostatic conductive layer 520, a passivation layer518, and a touch sensor 532.

The touch sensor 532 may be coupled to a top surface (e.g., a surfacefacing the input surface 508) of the cover sheet layer 522. The touchsensor 532 may be coupled to the cover sheet layer 522 through anadhesive layer 524, which may be an optically clear adhesive. In someembodiments, the adhesive layer 524 may be omitted and all or a portionof the touch sensor 532 may be formed directly on the cover sheet layer522 (e.g., by depositing an array of drive touch electrodes 526 directlyonto a bottom surface of the cover sheet layer 522).

An electrostatic conductive layer 520 may be coupled to the touch sensor532, and a passivation layer 518 may be coupled to the electrostaticconductive layer 520. An insulating substrate 534 may be positionedbetween the electrostatic conductive layer 520 and the touch sensor 532.In some embodiments, the electrostatic conductive layer 520 and thepassivation layer 518 may be formed separate from other components ofthe cover assembly 506, and the insulating substrate may be an adhesivelayer coupling the electrostatic conductive layer 520 and thepassivation layer 518 to the touch sensor 532.

In other embodiments, the insulating substrate 534 may be an epoxy orsimilar layer deposited over the touch sensor 532, which is then cured.The electrostatic conductive layer 520 and the passivation layer 518 maythen be deposited onto the insulating substrate 534 and cured to formhardened layers over the insulating substrate 534.

The electrostatic conductive layer 520 may be formed with conductiveparticles within a non-conductive compound, such as described furtherwith respect to FIG. 4. The passivation layer 518 may be formed withnon-conductive particles within a similar compound, such as describedfurther with respect to FIG. 4

The touch sensor 532 may include one or more drive touch electrodes 526and sense touch electrodes 530 separated by an insulating substrate 528.A drive touch electrode 526 may be coupled to a drive signal, which mayinduce an electric field, capacitively coupling the drive touchelectrode 526 to at least a portion of the electrostatic conductivelayer 520.

Due to the electric field coupling the drive touch electrode 526 to theelectrostatic conductive layer 520, the electrostatic conductive layer520 becomes electrostatically charged. The electrostatic chargegenerates or increases an attractive force between the electrostaticconductive layer 520 and a user's finger 512, which may be due to acapacitive coupling between the user's finger 512 and the electrostaticconductive layer 520. The passivation layer 518 may act as an insulatinglayer separating and facilitating the capacitive coupling of the user'sfinger 512 and the electrostatic conductive layer 520.

Other embodiments can implement haptic feedback in another manner. Forexample, FIGS. 6A-7B depict example cover assemblies incorporating apiezoelectric haptic element to provide vibratory and/or frictionfeedback at an input surface of an electronic device. A haptic outputcan, in some examples, be a localized decrease in perceived frictionbetween the user's finger and the interface surface. To generate thehaptic output, the input/output interface drives a piezoelectric bodybelow the interface surface at a high frequency (e.g., ultrasonic),thereby causing the interface surface to vibrate. As a result, when theuser's finger moves across the interface surface, the user may perceivedecreased friction due to decreased contact area or time between theuser's finger and the interface surface.

In this example, certain regions of the interface surface may beperceived to be higher friction regions (e.g., above a piezoelectricbody not driven or driven to a lower voltage, at a lower frequency, orat a lower duty cycle) whereas other regions may be perceived to belower friction regions (e.g., above a piezoelectric body to a highervoltage, at a higher frequency, or at a higher duty cycle).

In another example, the haptic output generated by an input/outputinterface can be a localized vibration, translation, or other mechanicalagitation of the interface surface. To generate the haptic output, theinput/output interface drives an electrode of a piezoelectric body belowthe interface surface at a low frequency (e.g., 100 Hz to 200 Hz),thereby mechanically agitating the interface surface. In this manner,when the user's finger moves across the interface surface, the user mayperceive a mechanical agitation of the interface surface such as aclick, a pop, a vibration, and so on.

FIGS. 6A-6B depict a cross-section of a cover assembly 606 particularlyillustrating electrodes of a touch sensor and a piezoelectric hapticelement disposed on the same surface. More particularly, the coverassembly 606 includes an insulating substrate 628 that separates a firstset of electrodes generally oriented in a first direction (one of whichis visible, and identified as a sense touch electrode 630) from a secondset of electrodes oriented in a second direction (one of which isidentified as a drive touch electrode 626, and another is identified asa drive haptic electrode 627). These components of the cover assembly606 can be positioned below and (optionally) adhered or otherwisecoupled to a cover sheet layer 622. The cover assembly 606 can beconfigured to detect touch input, and in some embodiments mayadditionally or alternatively detect force input.

In some embodiments, the first set of electrodes is orientedperpendicular to the second set of electrodes to define a grid ofoverlapping regions that may be individually addressable by couplingspecific electrodes of the first set and specific electrodes of thesecond set to drive and/or sense circuitry (e.g., coupling the drivetouch electrode 626 to drive circuitry and coupling the sense touchelectrode 630 to sense circuitry). In other examples, the first set ofelectrodes and/or the second set of electrodes can be arranged and/orsegmented in a different manner. For example, one or both of the firstset or the second set may be further segmented.

In this embodiment, the insulating substrate 628 of the cover assembly606 is formed from a piezoelectric material. Example piezoelectricmaterials include both leaded and lead-free niobates and titanates suchas PZT, KNN, NBT-BT, BCT-BZT, and so on. The piezoelectric material maybe transparent or opaque and can be disposed and/or formed using anysuitable technique such as, but not limited to, sputtering, physicallayer deposition, sol gel deposition/printing/gravure, and so on.

In some embodiments, each of the layers of the cover assembly 606 may bedeposited or otherwise formed onto the cover sheet layer 622. Forexample, the sense touch electrodes 630 may be deposited onto the coversheet layer 622 through an appropriate technique, such as vapordeposition, printing, gravure, roll-to-roll deposition, and so on. Theinsulating substrate 628 may then be deposited below the sense touchelectrodes 630. The drive touch electrodes 626 and drive hapticelectrodes 627 may then be formed on the insulating substrate 628,through an appropriate technique such as described with respect to thesense touch electrodes 630.

In other embodiments, the sense touch electrodes 630, drive touchelectrodes 626, and drive haptic electrodes 627 may be formed onto theinsulating substrate 628. This touch/haptic assembly may then be coupledto the cover sheet layer 622 through an optically clear adhesive oranother appropriate technique.

As a result of this construction, the cover assembly 606 can beconfigured to simultaneously receive user input and provide hapticoutput. More particularly, a first subset of electrodes of the first andsecond set of electrodes can be associated with haptic output while asecond subset of electrodes of the first and second set of electrodescan be associated with sensing input. For example, the drive hapticelectrode 627 (of the second set of electrodes) may be associated withhaptic output while the drive input electrode 626 is associated withtouch input and/or force input detection.

Haptic output can be provided by the piezoelectric body of theinsulating substrate 628 by applying a voltage across the insulatingsubstrate 628 via the drive haptic electrode 627 while, simultaneously,touch and/or force input are received via the drive input electrode 626.The sense touch electrodes 630 may provide a reference voltage for bothtouch sensing and haptic feedback.

In another embodiment, a cover assembly can provide piezoelectricfeedback through a separate layer from the touch sensor. Moreparticularly, FIG. 7A depicts a cover assembly 706 that includes a touchsensor 732, which may include a substrate separating two electrodelayers which have been omitted from FIG. 7A for clarity. The touchsensor 732 can be configured to detect touch input and/or force inputfrom a user. A haptic output module is positioned below the touch sensor732, separated by a stiffener layer 725.

The haptic output module includes a piezoelectric substrate 731separating a first and second set of electrodes. The piezoelectricsubstrate 731 may be formed from an appropriate piezoelectric material,similar to the insulating substrate 628 depicted in FIGS. 6A-6B. Thefirst set of electrodes, oriented along a first direction, areidentified as reference haptic electrodes 729. The second set ofelectrodes, oriented along a second direction transverse to the firstdirection, are identified as drive haptic electrodes 727.

As depicted in FIG. 7A, a display 704 is positioned below the coverassembly 706. Accordingly, the materials of the cover assembly 706 maybe optically transparent, including the touch sensor 732, the stiffenerlayer 725, the reference haptic electrodes 729, the piezoelectricsubstrate 731, and the drive haptic electrodes 727. These layers may beformed together as described above with respect to FIGS. 6A-6B.

For example, the stiffener layer 725 may be formed from glass, silicon,plastic, or another sufficiently rigid material. The touch sensor 732may be formed on a first surface of the stiffener 725. Some or all ofthe components of the haptic output module, such as the reference hapticelectrodes 729, the piezoelectric substrate 731, and the drive hapticelectrodes 727 may be formed on a second surface of the stiffener layer725. By coupling the haptic output module to the stiffener layer 725,the haptic effect of actuating the piezoelectric substrate 731 may beamplified.

As shown in FIG. 7B, in some examples the haptic output module may bepositioned below the display 704, while the touch sensor 732 ispositioned above the display 704. Accordingly, the stiffener layer 725may be below the display 704, and the reference haptic electrodes 729,the piezoelectric substrate 731, and the drive haptic electrodes 727 maybe coupled to or formed on the stiffener layer 725.

FIGS. 8A-8C depict example particle arrangements for an electrostaticconductive layer. The electrostatic conductive layer 820 includesconductive particles 838 and non-conductive particles 836 disposedwithin an organic matrix 840, which may be an epoxy. The electrostaticconductive layer 820 may be substantially as described above withrespect to FIG. 4, and may be formed by a method or technique similar tothat described below with respect to FIG. 10.

As described above, the conductive particles 838 and non-conductiveparticles 836 may be disposed within the organic matrix 840 in a mannerto ensure the electrostatic conductive layer 420 operates to producehaptic feedback and does not interfere with the operation of othercomponents. For example, as depicted in FIG. 8A, the conductiveparticles 838 and the non-conductive particles 836 may be evenlydispersed within the organic matrix 840 such that the conductiveparticles 838 are not concentrated in regions of the electrostaticconductive layer 820.

In some embodiments, the conductive particles 838 and non-conductiveparticles 836 may be patterned to enhance the operation of theelectrostatic conductive layer 820 and/or reduce interference with theoperation of other components. For example, as depicted in FIG. 8B, theelectrostatic conductive layer 820 may be patterned such that theconductive particles 838 are concentrated within conductive regionsformed as columns (or rows) which are separated by columns (or rows) ofnon-conductive particles 836.

In some embodiments, the columns of the conductive regions may be alongthe same direction as the drive touch electrodes of a touch sensor (suchas the drive touch electrodes 326 depicted in FIG. 3) and may bepositioned above and parallel to the drive touch electrodes. As anexample, alignment of the conductive particles 838 in the conductiveregions with the drive touch electrodes may enhance the capacitivecoupling between the conductive particles 838 and the drive touchelectrodes. In other embodiments the conductive particles 838 in theconductive regions may be offset from the drive touch electrodes, alonga different direction, or otherwise unaligned with the drive touchelectrodes to decrease interference with the operation of the touchsensor.

As another example, as depicted in FIG. 8C, the conductive particles 838may be concentrated into substantially equilateral conductive regions(e.g., square, round, or other geometric shapes), separated byconcentrations of non-conductive particles 836. In this pattern, theconductive particles 838 may be sufficiently concentrated within theconductive regions to provide electrostatic haptic feedback over thoseconductive regions, while leaving less concentrated regions foroperation of the touch sensor and other components to operate withoutinterference.

The conductive regions of concentrated conductive particles 838 depictedin FIG. 8C may effectively function as distinct electrodes, which mayadditionally enable the electrostatic conductive layer 820 to providelocalized frictional feedback over the conductive regions. For example,the conductive regions may correspond to drive touch electrodes arrayedas conductive pads, which may be separately driven to provide varyingelectrostatic haptic feedback over distinct portions of the inputsurface of the electronic device.

It should be understood that FIGS. 8A-8C are illustrative in nature. Anumber of other patterns and arrangements of conductive andnon-conductive particles within an epoxy may be used to create anelectrostatic conductive layer according to similar principles. Inaddition, the depicted conductive particles 838 and non-conductiveparticles 839 may be representative of areas with higher concentrationsof conductive particles and higher concentrations of non-conductiveparticles respectively. For example, the portions of the electrostaticconductive layer 820 depicted with only conductive particles 838 mayalso include non-conductive particles, but with relatively higherconcentrations of conductive particles 838.

FIG. 9A depicts a top view of an electronic device according to thepresent disclosure, illustrating electrostatic haptic feedback on aportion of an input surface. The electronic device 900 of FIG. 9Aincludes a housing 902 at least partially enclosing a display 904. Acover assembly 906 may be positioned over the display 904 and coupled tothe housing 902. The cover assembly 906 defines an input surface 908 forreceiving touch and/or force inputs to the electronic device 900.

The cover assembly 906 may also selectively provide electrostatic hapticfeedback to a user's finger 912 in contact with the input surface 908,such as through increased friction or similar sensations. Theelectrostatic haptic feedback may be provided through an electrostaticconductive layer in the cover assembly 906. The electrostatic conductivelayer may be energized by a drive touch electrode positioned below theelectrostatic conductive layer (e.g., as depicted above with respect toFIGS. 3 and 5).

As one or more drive touch electrodes are energized, the user's finger912 may experience the electrostatic haptic feedback at a feedbackregion 950, which may be a column across the input surface 908, whichmay correspond to the location of the drive touch electrode. In otherexamples, the drive touch electrode may be arranged in rows, and thefeedback region 952 of may be a row across the input surfacecorresponding to the activated drive touch electrode, such as depictedin FIG. 9B.

The sensation of the electrostatic haptic feedback in a feedback region950, 952 may controllably cause the perception of a rough sensation, oralternatively a sandy, wavy, or similar sensation. The sensations mayfurther be controlled to provide more or less intense sensations. Afeedback region 950, 952 may provide a constant frictional sensation, orthe type and intensity of the frictional sensation may vary over time.

Turning to FIG. 9C, another top view of an electronic device isdepicted, illustrating electrostatic haptic feedback on another portionof an input surface. In some embodiments, the electrostatic conductivelayer and/or the drive touch electrodes may be disposed and arranged toprovide more localized electrostatic haptic feedback. For example, thedrive touch electrodes may be substantially equilateral conductive padsarranged in a rectilinear pattern. The electrostatic conductive layermay also be patterned to concentrate conductive particles above thedrive touch electrodes.

Accordingly, when a drive signal activates a drive touch electrode,electrostatic haptic feedback may be produced at a substantiallylocalized feedback region 954. The feedback region 954 may correspond tothe size and/or shape of the drive touch electrode(s) which have beenactivated to induce the electrostatic haptic feedback. In someembodiments, additional feedback regions 956, 958 may also be producedby driving additional drive touch electrodes. In some examples, distinctdrive signals may drive the additional drive touch electrodes,generating distinct haptic feedback at the additional feedback regions956, 958.

FIG. 10 depicts an example method of forming a cover assembly for anelectronic device to provide electrostatic feedback. The method 1000 ofFIG. 10 may be implemented to form a cover assembly of an electronicdevice, which operates to produce electrostatic haptic feedback, such asdescribed in the examples depicted above with respect to FIGS. 1-9.

The method begins at operation 1002, in which a cover sheet is preparedfor forming electrostatic feedback layers, including an electrostaticconductive layer and/or a passivation layer. A cover sheet may be formedin a separate process, and may be formed from a suitable material, suchas glass, plastic, sapphire, or combinations thereof. At operation 1002,the cover sheet may be prepared for the addition of an electrostaticconductive layer.

In some embodiments, at operation 1002 the cover sheet may be roughenedthrough a chemical bath or mechanical process, which may introduceimperfections in a surface of the cover sheet to increase bondingbetween the cover sheet and the electrostatic conductive layer. In someembodiments, at operation 1002 the cover sheet may be treated through achemical or other process to strengthen the cover sheet. In an example,the cover sheet may be strengthened through an ion exchange, which mayplace the cover sheet under tension and/or compressive stress.

Next, at operation 1004, an epoxy (e.g., an organic matrix) for theelectrostatic conductive layer may be formed. At operation 1006,inorganic particles may be added to the epoxy. Prior to addition intothe epoxy, the inorganic particles may be prepared through anappropriate technique. In some examples, inorganic materials may beformed into the inorganic particles through a sol-gel process, through acalcination and pulverization process, or similar techniques.

The inorganic particles may include conductive particles andnon-conductive particles, which may be deposited in the epoxy at asufficient density such that the electrostatic conductive layer mayproduce electrostatic haptic feedback, but the conductive particles maybe sufficiently dispersed such that the electrostatic conductive layerdoes not interfere with the operation of other components of theelectronic device. In some example, the conductive and non-conductiveparticles may be arranged in patterns, which may be through preparingepoxies at distinct densities and depositing the epoxies in patterns atoperation 1008.

In some embodiments, both conductive and non-conductive particles may beadded to the epoxy at operation 1006. In other embodiments, the epoxymay be formed with precursors which form the epoxy and inorganicparticles in operation 1004. For example, the epoxy may be formed from amixture of tetramethoxysilane (TMOS), 3-glycidoxypropyl-trimethoxysilane(GPTMS), and titanium-tetraethylate (Ti(OEt)₄). After the epoxy andnon-conductive particle mixture is formed at operation 1004, conductiveparticles may be added to the epoxy mixture at operation 1006.

Next, at operation 1008, the epoxy is deposited over the cover sheet.The epoxy may be deposited using an appropriate technique, such as spincoating the cover sheet with the epoxy, spray coating, resin dispensing,and so on. In some examples, more than one epoxy may be formed inoperations 1004 and 1006, each epoxy having distinct concentrations ofconductive particles. At operation 1008, the different epoxies may bedeposited in a pattern, resulting in different concentrations ofconductive particles at different portions of the cover sheet.

Finally, at operation 1010 the epoxy may be cured. In some examples, theepoxy may be cured by heating the epoxy to an appropriate temperature,such as 110° C. After curing, the epoxy may form a cross-linked organicmatrix with the inorganic particles (including conductive andnon-conductive particles) embedded within the matrix.

As depicted in FIG. 10, once the epoxy is cured, the method 1000 mayreturn to operation 1004. One or more additional layers may be formedover the cured epoxy layer. For example, the electrostatic conductivelayer may be formed through multiple layers. In some examples, theelectrostatic conductive layer may be formed from a first layer withconductive particles at a first concentration and a second layer withconductive particles at a lower second concentration. Additional layersmay be included with distinct concentrations of conductive particles.

As another example, a passivation layer may be formed over theelectrostatic conductive layer through a similar method. The passivationlayer may be formed by forming an epoxy at operation 1004, which may beformed from the same or a different epoxy as the electrostaticconductive layer. At operation 1006, non-conductive organic particlesmay be added to the epoxy. However, as described above, by using certainprecursors at operation 1004 the non-conductive inorganic particles maybe formed into the epoxy in one operation, and operation 1006 may beomitted.

At operation 1008, the epoxy may be deposited over the electrostaticconductive layer through an appropriate technique, such as spin coating.The epoxy may be cured at operation 1010, producing a hardenedpassivation layer with non-conductive inorganic particles embeddedwithin an organic matrix.

One may appreciate that although many embodiments are disclosed above,the operations and steps presented with respect to methods andtechniques are meant as exemplary and accordingly are not exhaustive.One may further appreciate that alternate operation order or fewer oradditional operations may be required or desired for particularembodiments. For example, operation 1002, preparing the cover sheet, maybe omitted in some embodiments, or may occur concurrently with otheroperations. In another example, the operations of method 1000 may beperformed on a large cover sheet, which may afterward be cut intosmaller pieces to form cover sheets of electronic devices having anelectrostatic conductive layer and a passivation layer.

FIG. 11 depicts example components of an electronic device in accordancewith the embodiments described herein. The schematic representationdepicted in FIG. 11 may correspond to components of the devices depictedin FIGS. 1-10, described above. However, FIG. 11 may also more generallyrepresent other types of electronic devices with a cover assembly whichprovides electrostatic haptic feedback through a hybrid conductivecoating, which may include inorganic conductive and non-conductiveparticles within an organic matrix.

As shown in FIG. 11, a device 1100 includes a drive electrode 1126 and asense electrode 1130, which may form a drive touch electrode and sensetouch electrode of a touch sensor. The touch sensor may operate usingthe drive electrode 1126 and the sense electrode 1130 to determine alocation of a finger or touch over the input surface of the device 1100.The drive electrode 1126 and the sense electrode 1130 may operate inaccordance with a mutual-capacitance or self-capacitance touch sensingscheme.

In addition, the drive electrode 1126 may be driven with a haptic drivesignal (e.g., a haptic drive signal received from the signal generator1166) in order to provide an electrical field to activate a conductivelayer and provide electrostatic haptic feedback at an input surface ofthe device 1100. The haptic drive signal may induce a variableelectrostatic charge on the surface, which may produce sensations ofhigher and/or lower friction to a user operating the electronic device.

The device 1100 may also include a signal generator 1166. The signalgenerator 1166 may be operatively connected to the drive electrode 1126.The signal generator 1166 may transmit electrical signals to the driveelectrode 1126 to control the electrostatic haptic feedback generated atthe input surface. The signal generator 1166 is also operativelyconnected to processing circuitry 1160 and computer memory 1162. Theprocessing circuitry 1160 is configured to control the generation of theelectrical signals for the drive electrode 1126.

The memory 1162 can store electronic data that can be used by the signalgenerator 1166. For example, the memory 1162 can store electrical dataor content, such as timing signals, algorithms, and one or moredifferent electrical signal characteristics that the signal generator1166 can use to produce one or more electrical signals. The electricalsignal characteristics include, but are not limited to, an amplitude, aphase, a frequency, and/or a timing of an electrical signal. Theprocessing circuitry 1160 can cause the one or more electrical signalcharacteristics to be transmitted to the signal generator 1166. Inresponse to the receipt of the electrical signal characteristic(s), thesignal generator 1166 can produce an electrical signal that correspondsto the received electrical signal characteristic(s).

The processing circuitry 1160 is operatively connected to components ofthe device 1100, such as a signal generator and/or the drive electrode1126. In addition, the processing circuitry 1160 may be operativelyconnected to the computer memory 1162. The processing circuitry 1160 maybe operatively connected to the memory 1162 component via an electronicbus or bridge. The processing circuitry 1160 may include one or morecomputer processors or microcontrollers that are configured to performoperations in response to computer-readable instructions. The processingcircuitry 1160 may include a central processing unit (CPU) of the device1100. Additionally or alternatively, the processing circuitry 1160 mayinclude other processors within the device 1100 including applicationspecific integrated chips (ASIC) and other microcontroller devices. Theprocessing circuitry 1160 may be configured to perform functionalitydescribed in the examples above.

The memory 1162 may include a variety of types of non-transitorycomputer-readable storage media, including, for example, read accessmemory (RAM), read-only memory (ROM), erasable programmable memory(e.g., EPROM and EEPROM), or flash memory. The memory 1162 is configuredto store computer-readable instructions, sensor values, and otherpersistent software elements.

In this example, the processing circuitry 1160 is operable to readcomputer-readable instructions stored on the memory 1162. Thecomputer-readable instructions may adapt the processing circuitry 1160to perform the operations or functions described above with respect toFIGS. 1-10. The computer-readable instructions may be provided as acomputer-program product, software application, or the like.

The device 1100 may also include a battery 1168 that is configured toprovide electrical power to the components of the device 1100. Thebattery 1168 may include one or more power storage cells that are linkedtogether to provide an internal supply of electrical power. The battery1168 may be operatively coupled to power management circuitry that isconfigured to provide appropriate voltage and power levels forindividual components or groups of components within the device 1100.The battery 1168, via power management circuitry, may be configured toreceive power from an external source, such as an alternating currentpower outlet. The battery 1168 may store received power so that thedevice 1100 may operate without connection to an external power sourcefor an extended period of time, which may range from several hours toseveral days.

In some embodiments, the device 1100 also includes a display 1104 thatrenders visual information generated by the processing circuitry 1160.The display 1104 may include a liquid-crystal display, light-emittingdiode, organic light emitting diode display, organic electroluminescentdisplay, electrophoretic ink display, or the like. If the display 1104is a liquid-crystal display or an electrophoretic ink display, thedisplay may also include a backlight component that can be controlled toprovide variable levels of display brightness. If the display 1104 is anorganic light-emitting diode or organic electroluminescent type display,the brightness of the display 1104 may be controlled by modifying theelectrical signals that are provided to display elements.

In some embodiments, the device 1100 includes one or more input devices1110. The input device 1110 is a device that is configured to receiveuser input. The input device 1110 may include, for example, a pushbutton, a touch-activated button, or the like. In some embodiments, theinput devices 1110 may provide a dedicated or primary function,including, for example, a power button, volume buttons, home buttons,scroll wheels, and camera buttons. Generally, a touch sensor and a forcesensor may also be classified as input components. However, for purposesof this illustrative example, the drive electrode 1126 and senseelectrode 1130 of the touch sensor, as well as the force sensor 1172,are depicted as distinct components within the device 1100.

The device 1100 may also include a haptic actuator 1170. The hapticactuator 1170 may provide additional haptic feedback to a user throughvibratory or other haptic output. The haptic actuator may be implementedas a linear actuator, an eccentric rotational motor, a piezoelectrictransducer, and similar haptic technologies. The haptic actuator 1170may be controlled by the processing circuitry 1160 and/or the signalgenerator 1166, and may be configured to provide haptic feedback to auser interacting with the device 1100. In some embodiments, distinctsignal generators 1166 may be connected to the drive electrode 1126 andthe haptic actuator 1170.

The device 1100 may also include a communication port 1164 that isconfigured to transmit and/or receive signals or electricalcommunication from an external or separate device. The communicationport 1164 may be configured to couple to an external device via a cable,adaptor, or other type of electrical connector. In some embodiments, thecommunication port 1164 may be used to couple the device 1100 to aperipheral device or a computer.

The device 1100 also includes a force sensor 1172, which may registerthe application of force to the input surface of the device 1100. Theforce sensor 1172 may be a capacitive force sensor, a strain gauge, apiezoelectric force sensor, or another appropriate force-sensing device.In some embodiments, the force sensor 1172 may be a non-binary forcesensor, or a force sensor which measures an amount of force with a rangeof values. In other words, the force sensor may exhibit a non-binaryelectrical response (e.g., a change in voltage, capacitance, resistance,or other electrical parameter) indicating the amount of force applied tothe input surface of the electronic device.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of the specificembodiments described herein are presented for purposes of illustrationand description. They are not intended to be exhaustive or to limit theembodiments to the precise forms disclosed. It will be apparent to oneof ordinary skill in the art that many modifications and variations arepossible in view of the above teachings.

For example, features implementing functions may also be physicallylocated at various positions, including being distributed such thatportions of functions are implemented at different physical locations.Also, as used herein, including in the claims, “or” as used in a list ofitems prefaced by “at least one of” indicates a disjunctive list suchthat, for example, a list of “at least one of A, B, or C” means A or Bor C or AB or AC or BC or ABC (i.e., A and B and C). Further, the term“exemplary” does not mean that the described example is preferred orbetter than other examples.

What is claimed is:
 1. An electronic device, comprising: a housing; anda cover assembly coupled to the housing and comprising: a cover layer;an electrostatic output layer below the cover layer configured toreceive a voltage to capacitively couple to a user touching the coverlayer, the electrostatic output layer comprising: an epoxy layer coupledto the cover layer; an array of nonconductive particles disposed withinthe epoxy layer; an array of conductive particles dispersed to apredetermined density within the epoxy layer and among the array ofnonconductive particles; and a piezoelectric body below the cover layerand defining an upper surface and a lower surface; a first electrodegroup disposed on the upper surface; and a second electrode groupdisposed on the lower surface and comprising: a touch sense electrodecoupled to a capacitive touch sensor; and a haptic drive electrodeconfigured to apply a voltage across the piezoelectric body to generatehaptic feedback through the cover assembly.
 2. The electronic device ofclaim 1, further comprising processing circuitry coupled to the firstand second electrode groups.
 3. The electronic device of claim 2,wherein the processing circuitry is configured to apply the voltageacross the piezoelectric body in response to a touch.
 4. The electronicdevice of claim 1, wherein the touch sense electrode is disposedadjacent to the haptic drive electrode.
 5. The electronic device ofclaim 1, wherein: the touch sense electrode is a member of a set oftouch sense electrodes; and the haptic drive electrode is a member of aset of haptic drive electrodes.
 6. The electronic device of claim 5,wherein the set of haptic drive electrodes are interstitially disposedbetween the set of touch sense electrodes.
 7. The electronic device ofclaim 1, wherein the second electrode group is arranged as a set ofcolumns and the first electrode group is arranged as a set of rows,perpendicular to the set of columns.
 8. The electronic device of claim1, wherein the touch sense electrode has a first trace width and thehaptic drive electrode has a second trace width.
 9. The electronicdevice of claim 8, wherein the second trace width is greater than thesecond trace width.
 10. The electronic device of claim 1, wherein thefirst electrode group and the second electrode group are opticallytransparent.
 11. An electronic device, comprising: a transparent cover;an electrostatic output layer below the transparent cover configured toreceive a voltage to capacitively couple to a user touching thetransparent cover, the electrostatic output layer comprising: an epoxylayer coupled to and extending across the transparent cover; and anarray of conductive particles disposed at a predetermined density withina defined region of the epoxy layer; a display below the transparentcover defining an active display area below the epoxy layer of theelectrostatic output layer, the defined region within the active displayarea; a user input sensor positioned below the transparent cover andabove the display, the predetermined density selected to not interferewith operation of the user input sensor; a stiffener layer below theuser input sensor; a piezoelectric body below the user input sensor anddefining an upper surface and a lower surface; a haptic referenceelectrode group disposed on the upper surface; and a haptic driveelectrode group disposed on the lower surface and configured to apply avoltage across the piezoelectric body to generate haptic feedbackthrough the user input sensor and the transparent cover.
 12. Theelectronic device of claim 11, wherein the display is disposed below thepiezoelectric body.
 13. The electronic device of claim 11, wherein theuser input sensor is a force input sensor.
 14. The electronic device ofclaim 11, wherein the user input sensor is a touch input sensor.
 15. Theelectronic device of claim 11, wherein the display is disposed below thepiezoelectric body.
 16. The electronic device of claim 15, wherein thestiffener layer is positioned below the display.
 17. A cover assemblyfor an electronic device, comprising: a transparent cover layer; anelectrostatic output layer below the transparent cover layer configuredto receive a voltage to capacitively couple to a user touching thetransparent cover layer, the electrostatic output layer comprising: anepoxy layer coupled to the transparent cover layer; a nonconductiveparticle array disposed at a first density within the epoxy layer; and aconductive particle array disposed at a second density within the epoxylayer, the conductive particle array dispersed among the nonconductiveparticle array; a piezoelectric body below the transparent cover layerand the electrostatic output layer and defining an upper surface and alower surface; a first electrode group disposed on the upper surface;and a touch sense electrode group disposed on the lower surface andcoupled to a capacitive touch sensor; and a haptic drive electrode groupdisposed on the lower surface and arrange interstitially with the touchsense electrode group, the haptic drive electrode group configured toapply a voltage across the piezoelectric body to generate hapticfeedback through the cover assembly.
 18. The cover assembly of claim 17,further comprising a display positioned below the piezoelectric body.19. The cover assembly of claim 17, further comprising a stiffener layerpositioned above the piezoelectric body.
 20. The cover assembly of claim17, wherein the first electrode group is arranged perpendicular to thetouch sense electrode group and the haptic drive electrode group. 21.The cover assembly of claim 17, wherein the first density is differentfrom the second density.
 22. The cover assembly of claim 21, wherein thefirst density is greater than the second density.
 23. The cover assemblyof claim 21, wherein the conductive particle array is disposed at thesecond density within a defined region of the nonconductive particlearray.